Dichotomous branching occurs when the apical meristem divide into two identical parts that grow more less simultanously. In that type no branching is dominating (cotrary to monopodial branching for example). In bryophyta, Marchantia polymorpha is a good example.

Seta is the stem of the sporophyte of a bryophyte and it bears a sporangium. It's long and greenless in Bryopsida and Polytrichopsida. Sphagnopsida don't have seta and the sporangium is carried by a pseudopodium - the short stalk originating in gametophyte.

Operculum - in plants it is the cover of a sporangium. In higher bryophytes it's hidden under calyptra.

Apophysis is a swelling present just beneath the sporangium.

P.S. I am from Poland and, however we have courses in Polish but I want to know biology in English so I need to find all those things too. Regards